The present invention relates to a valve for changing the direction of flow of a fluid in pipe conduits conducting the fluid to and from a heat exchanger, respectively, said valve comprising a rotateable valve body and an enclosing valve house consisting of a cylindrical casing with end plates, wherein said valve body is rotatable around a rotary axis coinciding with a thought centre line of the cylindrical casing, and four flow passages extending through the valve house and being oriented in such a way that two diametrically located flow passages are approximately parallel with the rotary axis of the valve body and that the two other flow passages extend obliquely through the valve house, and, when the valve body is rotated into a first position, the flow passages connect a first connection port in the first end plate with a first connection port in the second end plate, and a second connection port in the first end plate with a second connection port in the second end plate, respectively, and, when the valve body is rotated into a second position, the flow passages connect a first connection port in the first end plate with a second connection port in the second end plate and a second connection port in the first end plate with a first connection port in the second end plate, respectively.
Heat exchangers used in systems in which cooling water is taken from natural water streams, river water, seawater etc. often show problems with clogging. Partly, it may depend on mud and particles jamming the cooling channels and partly on biological growth.
A simple and environmentally harmless way to keep a heat exchanger tolerably clean is to back flush the heat exchanger regularly, i.e. the direction of flow is reversed for example one or a few times each day. By reversing the direction of flow, mud and particles clogging the inlet region of the heat exchanger will be flushed out the same way it came in.
Back flushing of heat exchangers is also used to in some industrial processes in which fluids with large amounts of fibers are present, for example during the production of raw sugar. Fluid with cut down beats is to be heated and cooled in heat exchangers, and in order for the heat exchangers not to be clogged they must be back flushed regularly.
A back flushing valve of a similar kind as the one included by the invention, is previously known from for example SE 504 895, which describes a valve being used together with a heat exchanger to make back flushing possible. This valve consists of a valve house with a cylindrical casing and two end plates, and inside the valve house there is a rotatable valve body, by which the direction of flow can be reversed. The valve body in this valve has four flow passages and in order to keep the size of the valve down at least two of the flow passages have a non circular cross section in the middle portion of the valve body.